Modified constraint-induced movement therapy (mCIMT) improves upper limb (UL) function after stroke. Despite up to one-third of stroke survivors being eligible, clinical uptake remains poor. To address this, a multi-modal behaviour change intervention was implemented across a large seven-site early-supported discharge (ESD) rehabilitation service. This study investigated the acceptability of mCIMT implementation within this ESD service and identified adaptations required for sustained delivery. This qualitative study was nested within a mixed-methods process evaluation of mCIMT implementation. Four focus groups (n= 24) comprising therapists (two groups), therapy assistants (one group), and allied health managers (one group) were conducted. Data were analysed using reflexive thematic analysis and mapped to the Theoretical Domains Framework (TDF). Consumers were not directly involved in this study; however, lived experience research partners have helped shape the larger mixed-methods implementation study. Four themes were generated and mapped to the TDF. Factors related to acceptability included interdisciplinary practice in sharing workloads (belief about capabilities), practice opportunities across a range of UL presentations (skills), clinician attitudes influencing patient engagement (optimism), time constraints (belief about consequences), and cognitive overload from multiple systems and processes (memory, attention, and decision-making processes). Factors facilitating sustained delivery included improving stroke survivor education (knowledge), sharing success stories across teams (reinforcement), manager facilitation (social/professional role and identity), and the perception that the ESD setting was optimal for mCIMT delivery (social influences). mCIMT was acceptable in the ESD service, with clinicians feeling a responsibility to provide it. Key adaptations for sustained delivery included ongoing training, resource adaptation, and enhanced patient and carer engagement. Successful implementation and sustained delivery of mCIMT in the ESD service could enhance UL function and reduce the burden of care for potentially hundreds of stroke survivors and their carers. Modified constraint-induced movement therapy (mCIMT) helps improve arm movement after a stroke. However, many stroke survivors do not get this therapy. To fix this, we started a program in a large home-based rehabilitation service. This study looked at how well mCIMT could fit into this service. We also wanted to know what changes were needed to make sure it was regularly provided. We held four group discussions with therapists, therapy assistants, and health managers. A total of 24 people took part. From these discussions, we found several important points. Therapists needed to work together as a team. They also needed to practice mCIMT to get better at delivering it. Therapists having a positive attitude would encourage more stroke survivors to take part. For long-term success, stroke survivors need better education about mCIMT. Managers need to encourage therapists to provide mCIMT. The rehabilitation service should also share their success stories about this therapy to encourage therapists to deliver it and stroke survivors to ask for it. Therapists enjoyed delivering mCIMT in the rehabilitation service. It worked better than other therapies to improve a stroke survivor's arm function. Because of this, they also felt it was their duty to offer mCIMT. Having ongoing training and better resources would help keep mCIMT going. If mCIMT can be provided regularly in this service, it could lead to better arm function and less care needed for many stroke survivors and their carers.